The field of ophthalmic diagnostics includes both imaging based or structural techniques and functional approaches to diagnose and monitor various pathologies in the eye. One pathology of interest is glaucoma, an optic neuropathy resulting in characteristic visual field defects. It arises from progressive damage to the optic nerve (ON) and retinal ganglion cells (RGCs) and their axons, the retinal nerve fiber layer (RNFL). Investigating the relationship between development of functional damage in the visual field and structural glaucomatous changes of the RNFL has been the purpose of numerous studies [1-5].
Diagnostic instruments providing quantitative analyses in glaucoma assess either structural or functional aspects of the disease. Optical Coherence Tomography (OCT) is one technique capable of imaging the retina and providing quantitative analysis of RNFL measurements and measuring the optic nerve head. OCT is a noninvasive interferometric technique that provides cross sectional images and thickness measurements of various retinal layers including the RNFL (RNFLT) with high resolution [6] and good reproducibility [7-9]. Standard Automated white-on-white Perimetry (SAP) is the standard for assessing visual function by examination of the visual field. Parametric tests are able to provide quantitative measurements of differential light sensitivity at many test point locations in the visual field, and commercially available statistical analysis packages help clinicians in identifying significant visual field loss [10]. The diagnostic performance of both OCT and SAP in glaucoma as well as the correlation between SAP and OCT measurements has been investigated [11-14].
Clinical studies suggest that these diagnostic tests, used in isolation, provide useful information on the diagnosis and progression of the disease and, used in conjunction, provide supportive and complementing information which could lead to improved accuracy in disease detection and monitoring of progression. However, there is not one single diagnostic test used in isolation that provides adequate diagnostic accuracy and applicability across patient populations and disease dynamic range. It is therefore desirable to collect, display and analyze data from multiple ophthalmic diagnostic devices as is commercially available in the FORUM (Carl Zeiss Meditec, Inc. Dublin, Calif.) software package that allows customers to integrate and store ophthalmic diagnostic data from and analysis from multiple modalities and perform additional analysis on the combined data. It may also be desirable to display data from multiple diagnostic modalities on a single instrument so that the instrument operator can have the most complete picture of the patient for use in guiding the acquisition of data. Although the situation has been described in detail for glaucoma, the need for information from multiple modalities, including structural and functional measurements, which may complement each other and aid in diagnosis and treatment management decisions when reviewed together, is general to the ophthalmic field.
In commercially available ophthalmic diagnostic systems, the instrument operator typically selects from a series of scanning options based on known locations in the eye that may be relevant to a specific pathology. The data is displayed and analyzed in standard formats specified by the instrument manufacturer. As improvements in OCT technology allow for collection of larger volumes of data without appreciable patient motion artifacts, there is more and more data to be analyzed and interpreted. It is desirable to increase automation and interpretation in the display and analysis of these large volumes of data to improve and expand clinical applications of the technology.